Axial Fatigue of PBF-LB Ti6Al4V: Process and Surface Effects

This study investigates the influence of layer thickness and surface condition on the microstructure and mechanical performance of Laser Powder Bed Fusion (PBF-LB) manufactured Ti6Al4V. Specimens were produced using two layer thicknesses, 40~µm and 80~µm, under identical process parameters. Characterization included tensile and axial fatigue testing, supported by microstructural analysis using field-emission scanning electron microscopy (FE-SEM) and electron backscatter diffraction (EBSD). Both processing conditions produced fully martensitic α′ microstructures, with the 40~µm builds showing finer lamellae and smaller prior-β grains due to higher cooling rates. Tensile tests revealed higher ductility for the 40~µm specimens while maintaining similar strength levels. Axial fatigue tests revealed better performance for lower layer thickness, electropolished surface and diagonal orientation. The results confirm that fatigue performance in PBF-LB Ti6Al4V is primarily governed by surface integrity and defect population rather than changes in microstructural morphology. Overall, finer layers and surface finishing enhance endurance strength, though at the cost of reduced build productivity.